Glioblastoma (GBM) is most common central nervous system neoplasm in adults and one of the most aggressive and fatal malignancies in humans. The limited number of available therapies almost always fails, due to resistance of GBM stem cells (GSCs). We have found that expression of MNK kinases correlates with GBM grade and overall survival. Our studies demonstrate that these kinases play key and essential roles for survival of GSCs, raising the possibility that MNK targeting may provide a unique approach for the treatment of GBM. The current proposal aims to identify effector mechanisms by which MNK pathways promote GSC survival and to develop novel, specific, and effective MNK inhibitors that could be ultimately developed clinically for the treatment of GBM. Different GBM models and primary samples from GBM patients will be used for that purpose. Aim 1 will define MNK effector pathways in GSCs and will dissect their contributions in GBM pathophysiology. Experiments will be performed to define the roles of MNK-regulated effectors in controlling oncogenic mRNA translation, cell proliferation, and survival of GSCs. In addition, the differential requirement of MNK1 versus MNK2 in GSC growth and survival and their regulatory effects on downstream pathways will be dissected. Aim 2 will develop potent and selective MNK inhibitors through rational medicinal chemistry optimization. For this purpose, optimization of the MNK inhibitors that we have already developed will be pursued to improve potency, selectivity, and pharmaceutical properties. In addition, crystallization studies will be performed to understand the binding mode and support structure-based drug design. Aim 3 will evaluate the effects of MNK inhibition in orthotopic GBM mouse models. Compounds selected for adequate toxicity profiles and pharmacokinetics will be tested for efficacy against GBM using orthotopic xenograft mouse models for GBM. Altogether, the results of this work will provide important information on the mechanisms by which MNK kinases promote survival of GBM stem cells and will drive the development of novel pharmacological agents targeting the MNK kinase pathway for the treatment of GBM.